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authorQu Wenruo <wqu@suse.com>2024-09-02 06:59:06 +0200
committerDavid Sterba <dsterba@suse.com>2024-09-10 16:51:22 +0200
commitbd610c0937aaf03b2835638ada1fab8b0524c61a (patch)
tree9445683fc1ea1b80aa8bea50b43b48285021ca71 /fs/btrfs/extent_io.c
parentbtrfs: merge btrfs_folio_unlock_writer() into btrfs_folio_end_writer_lock() (diff)
downloadlinux-bd610c0937aaf03b2835638ada1fab8b0524c61a.tar.xz
linux-bd610c0937aaf03b2835638ada1fab8b0524c61a.zip
btrfs: only unlock the to-be-submitted ranges inside a folio
[SUBPAGE COMPRESSION LIMITS] Currently inside writepage_delalloc(), if a delalloc range is going to be submitted asynchronously (inline or compression, the page dirty/writeback/unlock are all handled in at different time, not at the submission time), then we return 1 and extent_writepage() will skip the submission. This is fine if every sector matches page size, but if a sector is smaller than page size (aka, subpage case), then it can be very problematic, for example for the following 64K page: 0 16K 32K 48K 64K |/| |///////| |/| | | 4K 52K Where |/| is the dirty range we need to submit. In the above case, we need the following different handling for the 3 ranges: - [0, 4K) needs to be submitted for regular write A single sector cannot be compressed. - [16K, 32K) needs to be submitted for compressed write - [48K, 52K) needs to be submitted for regular write. Above, if we try to submit [16K, 32K) for compressed write, we will return 1 and immediately, and without submitting the remaining [48K, 52K) range. Furthermore, since extent_writepage() will exit without unlocking any sectors, the submitted range [0, 4K) will not have sector unlocked. That's the reason why for now subpage is only allowed for full page range. [ENHANCEMENT] - Introduce a submission bitmap at btrfs_bio_ctrl::submit_bitmap This records which sectors will be submitted by extent_writepage_io(). This allows us to track which sectors needs to be submitted thus later to be properly unlocked. For asynchronously submitted range (inline/compression), the corresponding bits will be cleared from that bitmap. - Only return 1 if no sector needs to be submitted in writepage_delalloc() - Only submit sectors marked by submission bitmap inside extent_writepage_io() So we won't touch the asynchronously submitted part. - Introduce btrfs_folio_end_writer_lock_bitmap() helper This will only unlock the involved sectors specified by @bitmap parameter, to avoid touching the range asynchronously submitted. Please note that, since subpage compression is still limited to page aligned range, this change is only a preparation for future sector perfect compression support for subpage. Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/extent_io.c')
-rw-r--r--fs/btrfs/extent_io.c89
1 files changed, 51 insertions, 38 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 70be1150c34e..39c9677c47d5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -101,6 +101,13 @@ struct btrfs_bio_ctrl {
blk_opf_t opf;
btrfs_bio_end_io_t end_io_func;
struct writeback_control *wbc;
+
+ /*
+ * The sectors of the page which are going to be submitted by
+ * extent_writepage_io().
+ * This is to avoid touching ranges covered by compression/inline.
+ */
+ unsigned long submit_bitmap;
};
static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
@@ -1106,9 +1113,10 @@ int btrfs_read_folio(struct file *file, struct folio *folio)
*/
static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
struct folio *folio,
- struct writeback_control *wbc)
+ struct btrfs_bio_ctrl *bio_ctrl)
{
struct btrfs_fs_info *fs_info = inode_to_fs_info(&inode->vfs_inode);
+ struct writeback_control *wbc = bio_ctrl->wbc;
const bool is_subpage = btrfs_is_subpage(fs_info, folio->mapping);
const u64 page_start = folio_pos(folio);
const u64 page_end = page_start + folio_size(folio) - 1;
@@ -1123,6 +1131,14 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
u64 delalloc_to_write = 0;
int ret = 0;
+ /* Save the dirty bitmap as our submission bitmap will be a subset of it. */
+ if (btrfs_is_subpage(fs_info, inode->vfs_inode.i_mapping)) {
+ ASSERT(fs_info->sectors_per_page > 1);
+ btrfs_get_subpage_dirty_bitmap(fs_info, folio, &bio_ctrl->submit_bitmap);
+ } else {
+ bio_ctrl->submit_bitmap = 1;
+ }
+
/* Lock all (subpage) delalloc ranges inside the folio first. */
while (delalloc_start < page_end) {
delalloc_end = page_end;
@@ -1190,22 +1206,18 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
}
/*
- * We can hit btrfs_run_delalloc_range() with >0 return value.
- *
- * This happens when either the IO is already done and folio
- * unlocked (inline) or the IO submission and folio unlock would
- * be handled as async (compression).
- *
- * Inline is only possible for regular sectorsize for now.
- *
- * Compression is possible for both subpage and regular cases,
- * but even for subpage compression only happens for page aligned
- * range, thus the found delalloc range must go beyond current
- * folio.
+ * We have some ranges that's going to be submitted asynchronously
+ * (compression or inline). These range have their own control
+ * on when to unlock the pages. We should not touch them
+ * anymore, so clear the range from the submission bitmap.
*/
- if (ret > 0)
- ASSERT(!is_subpage || found_start + found_len >= page_end);
-
+ if (ret > 0) {
+ unsigned int start_bit = (found_start - page_start) >>
+ fs_info->sectorsize_bits;
+ unsigned int end_bit = (min(page_end + 1, found_start + found_len) -
+ page_start) >> fs_info->sectorsize_bits;
+ bitmap_clear(&bio_ctrl->submit_bitmap, start_bit, end_bit - start_bit);
+ }
/*
* Above btrfs_run_delalloc_range() may have unlocked the folio,
* thus for the last range, we cannot touch the folio anymore.
@@ -1230,10 +1242,10 @@ out:
DIV_ROUND_UP(delalloc_end + 1 - page_start, PAGE_SIZE);
/*
- * If btrfs_run_dealloc_range() already started I/O and unlocked
- * the folios, we just need to account for them here.
+ * If all ranges are submitted asynchronously, we just need to account
+ * for them here.
*/
- if (ret == 1) {
+ if (bitmap_empty(&bio_ctrl->submit_bitmap, fs_info->sectors_per_page)) {
wbc->nr_to_write -= delalloc_to_write;
return 1;
}
@@ -1331,15 +1343,6 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
unsigned long range_bitmap = 0;
- /*
- * This is the default value for sectorsize == PAGE_SIZE case.
- * We known we need to write the dirty sector (aka the page),
- * even if the page is not dirty (we cleared it before entering).
- *
- * For subpage cases we will get the correct bitmap later.
- */
- unsigned long dirty_bitmap = 1;
- unsigned int bitmap_size = 1;
bool submitted_io = false;
const u64 folio_start = folio_pos(folio);
u64 cur;
@@ -1357,18 +1360,14 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
return 1;
}
- if (btrfs_is_subpage(fs_info, inode->vfs_inode.i_mapping)) {
- ASSERT(fs_info->sectors_per_page > 1);
- btrfs_get_subpage_dirty_bitmap(fs_info, folio, &dirty_bitmap);
- bitmap_size = fs_info->sectors_per_page;
- }
for (cur = start; cur < start + len; cur += fs_info->sectorsize)
set_bit((cur - folio_start) >> fs_info->sectorsize_bits, &range_bitmap);
- bitmap_and(&dirty_bitmap, &dirty_bitmap, &range_bitmap, bitmap_size);
+ bitmap_and(&bio_ctrl->submit_bitmap, &bio_ctrl->submit_bitmap, &range_bitmap,
+ fs_info->sectors_per_page);
bio_ctrl->end_io_func = end_bbio_data_write;
- for_each_set_bit(bit, &dirty_bitmap, bitmap_size) {
+ for_each_set_bit(bit, &bio_ctrl->submit_bitmap, fs_info->sectors_per_page) {
cur = folio_pos(folio) + (bit << fs_info->sectorsize_bits);
if (cur >= i_size) {
@@ -1421,6 +1420,7 @@ out:
static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl)
{
struct inode *inode = folio->mapping->host;
+ struct btrfs_fs_info *fs_info = inode_to_fs_info(inode);
const u64 page_start = folio_pos(folio);
int ret;
size_t pg_offset;
@@ -1442,11 +1442,16 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl
if (folio->index == end_index)
folio_zero_range(folio, pg_offset, folio_size(folio) - pg_offset);
+ /*
+ * Default to unlock the whole folio.
+ * The proper bitmap can only be initialized until writepage_delalloc().
+ */
+ bio_ctrl->submit_bitmap = (unsigned long)-1;
ret = set_folio_extent_mapped(folio);
if (ret < 0)
goto done;
- ret = writepage_delalloc(BTRFS_I(inode), folio, bio_ctrl->wbc);
+ ret = writepage_delalloc(BTRFS_I(inode), folio, bio_ctrl);
if (ret == 1)
return 0;
if (ret)
@@ -1466,8 +1471,11 @@ done:
mapping_set_error(folio->mapping, ret);
}
- btrfs_folio_end_writer_lock(inode_to_fs_info(inode), folio,
- page_start, PAGE_SIZE);
+ /*
+ * Only unlock ranges that are submitted. As there can be some async
+ * submitted ranges inside the folio.
+ */
+ btrfs_folio_end_writer_lock_bitmap(fs_info, folio, bio_ctrl->submit_bitmap);
ASSERT(ret <= 0);
return ret;
}
@@ -2210,6 +2218,11 @@ void extent_write_locked_range(struct inode *inode, const struct folio *locked_f
if (pages_dirty && folio != locked_folio)
ASSERT(folio_test_dirty(folio));
+ /*
+ * Set the submission bitmap to submit all sectors.
+ * extent_writepage_io() will do the truncation correctly.
+ */
+ bio_ctrl.submit_bitmap = (unsigned long)-1;
ret = extent_writepage_io(BTRFS_I(inode), folio, cur, cur_len,
&bio_ctrl, i_size);
if (ret == 1)